Integrated Motor-Pump

ABSTRACT

An integrated motor-driven pump is proposed that reduces the part count of the assembly and addresses several tolerance and alignment issues by combining the outlet plate and retainer ring of the pump into a single component. The integrated motor-driven pump may also include an axial bushing for support of the motor shaft and inner gerotor, ensuring concentric rotation of these components. Combining one of the inlet or outlet plates with the retainer ring and including a central bushing eliminates the need for alignment pins and complex assembly procedures. The disclosure also combines one of the motor end plates with the disclosed integrated pump inlet or outlet plate, retainer ring and central bushing, eliminating the need for a separate motor end plate and bushing to support the motor shaft.

BACKGROUND

This disclosure relates to compact configurations for combining a pumpstage with a motor.

Compact motor-driven pumps are commonly employed to deliver fuel,lubricants, hydraulic or other fluids in equipment, land and watervehicles and aircraft. The pumps and motors are commonly manufacturedseparately and then assembled into the same housing, which may alsoserve as a conduit for fluid being pumped. The fluid being pumped maycirculate through the motor to lubricate and cool the motor andelectronics associated with a brushless motor configuration.

Roller vane, gerotor and turbine pump stages are commonly employed insuch assemblies, with the pump stage selected based on thecharacteristics of the fluid being pumped and the pressure and volume offluid flow required by the system. In the case of roller vane andgerotor pump designs, the pump stage typically includes three componentsthat define a pumping chamber. An inlet plate defines one or morearcuate inlet ports for fluid to enter the pumping chamber and definesone axial side of the pumping chamber. An outlet plate defines one ormore arcuate outlet ports and defines the opposite axial side of thepumping chamber. A retainer ring is sandwiched between the inlet andoutlet plates and defines the radial, inside surface of the pumpingchamber. In roller vane and gerotor pumps, the inside surface of thepumping chamber is defined by a circle eccentric from the center(rotational) axis of the motor and pump. The position of the inlet andoutlet ports, in combination with eccentrically rotating roller vane orgerotor pump components, result in differential pressures in the pumpchamber that force fluid through the pump from the inlet to the outlet.Pumped fluid may be directed through the motor for the purpose ofcooling and lubrication.

With respect to gerotor pumps in particular, the geometry and alignmentof pump components is critical to smooth and reliable pump operation.One important relationship is the rotational axis of the inner gerotorand rotational axis of the motor shaft, which are preferably concentric(as close to the same axis as possible). Most gerotor pumps employseparately manufactured inlet and outlet plates axially spaced by theretainer ring. Separately manufactured parts must be tightly toleranceto prevent tolerance stack up issues that will interfere with propergerotor pump operation. Further, the separate components must becarefully aligned during assembly to ensure a concentric relationshipbetween the motor shaft, the inner gerotor and the eccentric path of theouter gerotor. Alignment is typically accomplished by pins or fastenersextending axially through the inlet plate, retainer ring, and outletplate. Other unique assembly methods may be employed to ensure correctalignment of the several components. The inner gerotor may be centeredon a bushing pin supported by one of the inlet or outlet plates.Alternatively, the inner gerotor may be supported by the motor shaftitself, depending upon the size of the motor shaft. Separatelymanufactured components with alignment structures may complicatemanufacturing, assembly, and increase costs and have a potentiallynegative impact on reliability.

SUMMARY

An integrated motor-driven pump is proposed that reduces the part countof the assembly and addresses several tolerance and alignment issues bycombining the outlet plate and retainer ring of the pump into a singlecomponent. The integrated motor-driven pump may also include an axialbushing for support of the motor shaft and inner gerotor, ensuringconcentric rotation of these components. Combining one of the inlet oroutlet plates with the retainer ring and including a central bushingeliminates the need for alignment pins and complex assembly procedures.The disclosure also combines one of the motor end plates with thedisclosed integrated pump inlet or outlet plate, retainer ring andcentral bushing, eliminating the need for a separate motor end plate andbushing to support the motor shaft.

The disclosed motor-driven pump preferably employs a brushless motorconfiguration and directs pumped fluid through the motor for cooling andlubrication. Pumped fluid may also be directed to cool the controlelectronics which drive the brushless motor, directly or indirectly. Themotor end plate is formed as a single component with one of the pumpinlet or outlet plates, and incorporates the retainer ring and a centralbushing to support both the motor shaft and inner gerotor. The pumpstage may include as few as three components; the inner gerotor, outergerotor and one plate of the pump (typically the inlet plate, which mayalternatively be referred to as the inlet manifold.

In one embodiment, a motor end plate is adapted to serve as the inlet oroutlet plate of a pump secured to an axial end of the motor driving thepump.

In one embodiment, a motor end plate is integrated with an inlet oroutlet plate of a pump, a guide ring of the pump and bushings to supportthe motor shaft and rotating pump parts.

Alternative embodiments of the disclosed integrated motor pump mayincorporate one or more of the disclosed features and relationshipsincluded in the detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially exploded view of a first embodiment of a gerotorpump partially integrated with an electric motor; and

FIG. 2 is a sectional view through the gerotor pump partially integratedwith an electric motor as shown in FIG. 1;

FIG. 3 is a second embodiment of a gerotor pump integrated with anelectric motor;

FIG. 4 is a sectional view through the gerotor pump integrated with anelectric motor as shown in FIG. 3, and

FIGS. 5 and 6 are perspective views of the combined motor end plate,pump outlet plate, central bushing and pump retainer ring of theembodiment shown in FIGS. 3 and 4.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

A first embodiment of a gerotor pump 10 partially integrated with itsdrive motor 20 is illustrated in FIGS. 1 and 2. A second embodiment of agerotor pump 110 integrated with its drive motor 120 is illustrated inFIGS. 3-6. Both embodiments are compatible with brushed or brushless DCmotors, where the motor is assembled into a cylindrical housing andincludes motor end plates spanning each longitudinal end of the housing.The motor end plates typically include bushings for supporting the motorshaft and openings to allow fluid being pumped to pass through the motorassembly between the rotor and stator and over the bushings to lubricateand cool the motor assembly during use.

FIG. 1 illustrates an embodiment where an end plate 22 of the motor isformed as an outlet plate of the pump stage. This configurationeliminates the manufacture of a separate motor end plate in addition tothe pump outlet plate. In the embodiment of FIG. 1, the motor end plate22 includes at least one outlet port 24 configured to direct fluid fromthe gerotor set into the cylindrical motor housing 26, where fluid flowsbetween the rotor 36 and stator 30, as well as over the bushings 32, 34that support both ends of the motor shaft 28 (Depicted in FIG. 2). Thegerotor pump 10 also includes an inlet plate (or manifold) 12 with aninlet opening 15, a retainer ring 14, an outer gerotor 16, an innergerotor 17, and a motor coupling 18. A pair of alignment pins 40 aid inaligning the retainer ring 14 with the inlet and outlet plates 12, 22,in turn also providing alignment between the inner gerotor 17 and motorshaft 28. A bushing 13 seated in the inlet plate 12 supports the innergerotor 17 for rotation within the pumping chamber. The retainer ringinner surface 19 supports the outer geroter 16. The retainer ring innersurface 19 defines a circle that is eccentric to the axis of motor shaftrotation and the outside surface of bushing 13. Fasteners 42 secure thepump stage 10 to the motor end plate/outlet plate (or manifold) 12.

The disclosed combined motor end plate/outlet manifold 22 is constructedof materials and surface properties compatible with its function as aworking surface of a gerotor pump 10. The material must be resistant towear and begin with a planar (flat) surface that will cooperate withadjacent surfaces of the gerotor set to define differential pressurezones within the pump 10. Suitable materials include steel or alloy thatis cast or machined and finished to the correct dimensions. Powderedmetallurgy may also be employed to form parts such as the combined motorend plate/outlet manifold/retainer ring component 150 of the embodimentshown in FIGS. 5 and 6, as well as the inner and outer gerotors 16, 17,116, 117. The steel or alloy may begin as sheet or bar stock, which iscut and finished by methods known in the art. Tolerance stack in boththe axial and radial direction can impact gerotor operation, so formingseveral support surfaces on the same component should reduce tolerancevariation and improve pump operation and reliability.

It will be observed that, in the embodiment of FIGS. 1 and 2, the motorshaft 28, inner gerotor 17, and outer gerotor 16 are supported forrotation by different components, making it more challenging to ensurethat the motor shaft 28 and inner gerotor 17 are truly concentric, andthe proper eccentric is provided to guide rotation of the outer gerotor16. In the embodiment of FIGS. 1 and 2, the motor coupling 18 isdesigned to allow for some misalignment of the motor shaft 28 with theaxis of rotation of the inner gerotor 17. While the embodiment of FIG. 1does reduce part count relative to some prior art configurations,further improvements may be possible.

The embodiment of FIGS. 3-6 integrates the retainer ring with the pumpoutlet plate and arranges the combined structure 150 to serve as one ofthe motor end plates. As best shown in FIG. 4, the center of thecombined retainer ring and outlet plate includes a radially insidesurface 152 that locates a bushing to support the motor shaft 128. Thecenter of the combined retainer ring and outlet plate 150 also includesa boss 154 having a radially outside surface 156 that is arranged tosupport the inner gerotor 117. The same structure supports both themotor shaft 128 and inner gerotor 117. The motor shaft 128 extendsthrough the center of the combined retainer ring and outlet plate 150 toengage the inner gerotor 117 and apply rotational force to the gerotorset during operation. The integral retainer ring inside surface 119defines a circle that is eccentric relative to the axis of motor shaftrotation and the outside surface 156 of the center boss 154 whichdefines the axis of rotation of the inner gerotor 117. Rotation of thegerotor set within the integral retainer ring 150 produces differentialpressures that draw fluid in through the inlet openings 115 in the inletplate 112 and force fluid out through the outlet openings 124 in theoutlet plate integral to the retainer ring 150. In the depictedembodiment, the integral retainer ring outside surface 151 radiallyaccommodates the cylindrical motor housing 126.

Comparison of FIGS. 1 and 3 show the dramatic reduction in part count ofthe second embodiment of FIGS. 3-6 relative to the first embodiment ofFIG. 1. The integral retainer ring 150 and central boss 154 thatsupports both the motor shaft 128 and the inner gerotor 117 reduce theparts necessary to ensure concentricity of rotation for the pumpcomponents relative to the motor shaft 128. Precise positioning of thepump and motor components ensures smooth and reliable operation of themotor driven pump.

The disclosed concept for integrating a compact pump with an electricmotor is discussed in the context of a gerotor pump, but is not limitedto only this pump configuration. Other compact pump configurationsemploy an eccentric surface to guide pump components or to direct fluidflow through the pump and may advantageously employ the disclosedconcepts. Such pumps include, but are not limited to vane and rollervane pumps.

What is claimed:
 1. A motor-driven pump comprising: a motor having anexterior housing surrounding a stator and a rotor supported on a shaft,said motor having a first end plate with a first bushing supporting theshaft at a first end, and a second end plate having a second bushingsupporting the shaft at a second end, said shaft passing through saidsecond end plate, said second end plate including an integrally formedretainer ring and a central boss, both said central boss and saidretainer ring projecting axially away from said motor to define a pumpcavity, said retainer ring having an inside surface defined by a circleeccentric to an axis of rotation of said motor shaft, said central bossincluding an outside surface concentric with the axis of rotation ofsaid motor shaft; a pump rotor received in said pump cavity and seatedon said central boss; one or more pump components engaged with saidretainer ring inside surface to produce differential pressures withinsaid pump cavity during rotation of said pump rotor; and a pump inletplate secured to said retainer ring to retain said pump rotor andcomponents in said pump cavity.
 2. The motor-driven pump of claim 1,wherein said pump rotor is the inner rotor of a gerotor pump and saidone or more pump components are the outer gerotor of a gerotor pump. 3.The motor-driven pump of claim 1, wherein said pump rotor includesradial slots and said components are roller vanes of a roller vane pump.